The present disclosure relates generally to force feedback systems associated with computer-assisted surgery (“CAS”) systems and, more particularly, to systems and methods for customizing interactive haptic boundaries associated with CAS systems based on patient-specific information.
The knee joint comprises the interface between the distal end of the femur and the proximal end of the tibia. In a properly-functioning knee joint, medial and lateral condyles of the femur pivot smoothly along menisci attached to respective medial and lateral condyles of the tibia. When the knee joint is damaged, the natural bones and cartilage that form the joint may be unable to properly articulate, which can lead to joint pain and, in some cases, interfere with normal use of the joint.
In some situations, surgery is required to restore normal use of the joint and reduce pain. Depending upon the severity of the damage, the surgery may involve partially or completely replacing the joint with prosthetic components. During such knee replacement procedures, a surgeon resects damaged portions of the bone and cartilage, while attempting to leave healthy tissue intact. The surgeon then fits the healthy tissue with artificial prosthetic components designed to replicate the resected tissue and restore proper knee joint operation.
Typically, prior to the surgery, the surgeon develops a preliminary (“pre-operative”) plan that serves as a guide to performing the surgery. As part of the pre-operative planning, the surgeon surveys, among other things, the size, shape, kinematic function, and condition of the patient's joint. Using computer-assisted surgery systems, this survey can be performed by obtaining computer-based images of the joint and generating a computer-based model of the joint of the patient in virtual software space. Using this virtual model, the surgeon can evaluate the condition of the anatomic features of the joint and plan, among other things, the location and amount of bone that needs to be removed and the position and orientation in which the prosthetic components should be implanted on the bone to restore normal joint functionality.
Although the surgeon has a great degree of flexibility in customizing most aspects of the surgery based on the unique anatomy of the patient, the surgeon is typically limited to selecting from among a finite number of different prosthetic implant components. In many situations, a surgeon performs surgery on a patient whose anatomy does not precisely match any of the available prosthetic implant components. As a result, the surgeon may select a prosthetic implant that most closely fits—but does not precisely match—the patient's anatomy. The surgeon can then modify the surgical plan (either pre or intra-operatively) to accommodate for the selected prosthetic components.
In some situations, the CAS system may include a force feedback control system that is coupled to one or more surgical instruments (e.g., cutting tools) and configured to provide force feedback for controlling the surgical instrument during the surgery. The force feedback control system may constrain the cutting tool to limit the position or operation of the surgical instrument to within certain predefined boundaries. By allowing users to strategically define the placement of the virtual boundaries associated with the force feedback control system, these CAS systems enable surgeons to precisely and accurately control the resection and sculpting of the bone in preparation for receiving the prosthetic implant.
Because CAS systems provide a solution for accurately, reliably, and precisely executing bone cuts by defining the boundaries at which a cutting surface of a surgical instrument can operate, some CAS systems now include virtual software models that match the size and shape of available prosthetic implants. The virtual software model of the implant(s) can be positioned (in software) relative to the virtual model(s) of the patient's joint prior to or during the surgical procedure. Once positioned, the software model of the implant may be “registered” to the virtual model of the patient's anatomy so that the cutting surface is constrained to operate only within the area defined by the software model of the implant, limiting tissue removal only to the specific area of the patient's bone associated with the registered placement of the implant.
Systems that provide virtual models, and corresponding haptic boundaries, associated with a selection of available implants may allow surgeons to quickly and efficiently define a resection pattern for preparing the bone to receive the implant. Generally, each virtual implant model may be associated with a corresponding fixed haptic boundary, which may be based on the size and shape to the geometry associated with the virtual implant model. However, in some situations the surgeon selects an undersized prosthetic implant, but nonetheless wishes to remove areas of diseased or damaged tissue that may be located beyond the boundaries required to accommodate the undersized prosthetic implant.